Computer Networks · topic
Stop-and-wait, Go-Back-N and Selective Repeat efficiency, windows and sequence-number bits; UDP and TCP headers, the three-way handshake and teardown, byte sequence numbers and ACKs; TCP flow control with the receive window, sequence wrap, RTO estimation, throughput formulas; congestion control with slow start, avoidance, fast retransmit and fast recovery traced round by round.
Flow control with acknowledgements: stop-and-wait with timeouts and a one-bit sequence number, the ratio a of propagation to transmission time, efficiency of stop-and-wait and of a sliding window of W frames with the timeline that explains it, throughput, the window that fills the pipe (also when RTT is given directly), and the corrections for a non-zero ACK and for frame loss. Worked chains and two solved past questions (2025, 2026), all checked by script.
A partial preview of the top of the sheet. The full sheet is in the Computer Networks cheat sheet pack.
Sliding-window protocols for GATE CS: Go-Back-N and Selective Repeat compared on sender and receiver windows, acknowledgements, timers, buffering and what is resent after a loss; the sequence-number bounds and why a larger window breaks them (shown with 2-bit numbers); bits needed for a given window; and retransmission counts after a lost frame, from an event simulation in a script.
A partial preview of the top of the sheet. The full sheet is in the Computer Networks cheat sheet pack.
UDP (RFC 768) and TCP (RFC 9293) for GATE CS: header fields and sizes, what each service does and does not give, the three-way handshake and four-segment teardown with every sequence and acknowledgement number on a timeline, the connection states including TIME-WAIT, byte numbering with SYN and FIN each taking one number, cutting a stream into MSS-sized segments, and two solved past questions on the handshake (2024, 2025). Every number checked by script.
A partial preview of the top of the sheet. The full sheet is in the Computer Networks cheat sheet pack.
TCP flow control for GATE CS: the receive window and the sender's limit min(cwnd, rwnd), zero windows and the persist timer, window-limited throughput W/RTT and window scaling, how long the 32-bit sequence space lasts and the bits a fast link needs (two solved past questions, 2022 and 2026), retransmission-timeout estimation by RFC 6298 and by the older exponential average with Karn's rule and backoff, and the throughput models with their assumptions. Every value checked by script.
A partial preview of the top of the sheet. The full sheet is in the Computer Networks cheat sheet pack.
TCP congestion control for GATE CS: the round-by-round convention used in exam questions (slow start doubling capped at ssthresh, additive increase, ssthresh set to half of cwnd on loss), the exact per-ACK rules of RFC 5681 beside it, timeout versus three duplicate ACKs, Tahoe versus Reno, fast retransmit and fast recovery with window inflation, the initial window, the receive-window cap, and three solved past questions (2024, 2026). Includes a cwnd chart; every trace comes from a script.
A partial preview of the top of the sheet. The full sheet is in the Computer Networks cheat sheet pack.
